package com.cs;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Arrays;

/**
 * @ClassName: ScatteringAndGatheringTest
 *
 * Scattering: 将数据写入到buffer时，可以采用buffer数组，依次写入(分散)
 * Gathering：从buffer读取数据时，可以采用buffer数组，依次读
 *
 * 这个需要再次查看
 *
 * @Description: TODO
 * @Author: kevin
 * @Date: 2020/8/7 10:09
 * @Version: 1.0
 */
public class ScatteringAndGatheringTest {

    public static void main(String[] args) throws Exception {

        // 使用ServerSocketChannel 和SocketChannel
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        InetSocketAddress inetSocketAddress = new InetSocketAddress(7000);

        // 绑定端口到socket，并启动
        serverSocketChannel.socket().bind(inetSocketAddress);

        // 创建buffer数组
        ByteBuffer[] byteBuffers = new ByteBuffer[2];
        byteBuffers[0] = ByteBuffer.allocate(5);
        byteBuffers[1] = ByteBuffer.allocate(3);

        // 等待客户端连接（telnet）
        SocketChannel socketChannel = serverSocketChannel.accept();
        // 假定从客户端接收8个字节
        int messageLength = 8;
        // 循环读取
        while (true) {
            int byteRead = 0;

            while (byteRead < messageLength) {
                long l = socketChannel.read(byteBuffers);
                // 累计读取的字节数
                byteRead += l;
                System.out.println("byteRead=" + byteRead);
                // 使用流打印，看看当前buffer的position和limit
                Arrays.asList(byteBuffers).stream().map(buffer -> "position=" + buffer.position() +
                        ", limit=" + buffer.limit()).forEach(System.out::println);

            }
            // 将所有的buffer进行flip
            Arrays.asList(byteBuffers).forEach(buffer -> buffer.flip());

            // 将数据读出显示到客户端
            long byteWrite = 0;
            while (byteWrite < messageLength) {
                long l = socketChannel.write(byteBuffers);
                byteWrite += l;
            }

            // 将所有的buffer进行clean
            Arrays.asList(byteBuffers).forEach(buffer -> buffer.clear());

            System.out.println("byteRead=" + byteRead + " byteWrite=" + byteWrite + " messageLength=" + messageLength);
        }
    }
}
